XEKOPHYTE ASSOCIATIONS 231 



areas of dry naked soil are sometimes occupied by forest 

 growths that show no development of leaves, the tree- 

 like forms appearing continually bare. The oriental leaf- 

 less tree form is mostly a ('asuarina. Bordering the Gulf 

 of California, both in Mexico proper and in Lower Cali- 

 fornia, there are leafless forests composed of various kinds 

 of giant cactus (see Fig. 192), known as the "cardon 

 forests." These leafless forests represent the most extreme 

 xercphyte conditions occupied by plant forms that may 

 be regarded as trees. 



164. Salt steppes. — In addition to the xerophyte associa- 

 tions enumerated above, in which the water, though scanty, 

 is fresh, the two following may be considered. The soil 

 and air are relatively dry, as in ordinary xerophytic condi- 

 tions, but the water is more or less saturated with common 

 salt or alkaline salts. The salt steppes are interior arid 

 wastes, which probably mark the position of old sea basins. 

 In the United States one of the most extensive of the salt 

 steppes is in the Great Salt Lake basin (see Fig. 202). It 

 is here that members of the chenopod family are especially 

 at home, such as greasewoods, seablights, samphires, etc., 

 for more than any other plants have they learned to endure 

 such extremely unfavorable conditions. An extensive alka- 

 line waste in the United States is that known as the Bad 

 Lands, which stretches over certain portions of Nebraska 

 and Dakota, and in which the waters are strongly alkaline. 

 165. Salt and alkaline deserts. — In these areas the water 

 supply reaches its minimum, and therefore the water be- 

 comes saturated with the characteristic salts of the soil. 

 Xo worse combination for plant activity can be imagined 

 than the combination of minimum water and maximum 

 salts. In consequence, such areas are almost, if not abso- 

 lutely, devoid of vegetation. As illustrations, the exten- 

 sive desert of the Dead Sea region and the Death's Valley 

 in Southern California may be cited. 



